Cultural enrichment in Germany

More religion of peacefulness in Hamburg today:

A machete-wielding man has killed one and injured several others after going on the rampage through a German supermarket this afternoon. The attacker, who reportedly screamed Allahu Akbar, ran into an Edeka shop in the northern city of Hamburg before knifing customers and going on the run.

Witnesses followed him and raised the alarm at about 3.10pm before police swooped to  make an arrest. Heavily armed police have locked the area down and police helicopters have been seen above the crime scene. A motive for the knifing has not yet been established.

What could it possibly be?